1. Field of the Disclosure
The present invention relates to liquid crystal lens electrically driven, and more particularly, to a liquid crystal lens electrically driven in which micro division electrodes are applied both to upper and lower substrates, and a voltage condition is varied with a number of views of a stereo 3D image display for enabling display of a plurality of views and a stereoscopic display device thereof.
2. Discussion of the Related Art
It is foreseen that services to be realized for making faster information transmission to be constructed based on a super fast communication network will develop from the present simple “hearing and speaking” services such as telephone services to “watching and hearing” multimedia type services centered on digital terminals which process characters, voices and picture at a high speed, and finally to super spatial realistic three dimensional stereoscopic information communication services in which “watching, feeling and enjoying realistically and stereoscopically transcending time and space”.
In general, a stereo 3D image which expresses three dimension is made by a principle of a stereoscopic view angle through the two eyes in which a left eye and a right eye see images slightly different from each other owing to a difference of positions of the two eyes as the two eyes have a difference of views, i.e., the two eyes are about 65 mm spaced from each other. The difference of images caused by the difference of the two eyes is called as binocular disparity. A three dimensional stereoscopic display device makes a user to have a stereoscopic feeling owing to the binocular disparity by making the left eye to see an image only on the left eye and the right eye to see an image only on the right eye by using the binocular disparity.
That is, the left/right eyes are made to see two dimensional images different from each other respectively, and if the two images are transmitted to a brain through a retina, the brain combines the two images accurately to produce a sense of depth and a sense of reality of an original three dimensional image. Such a capability is in general called as stereography, and a device having the stereography applied thereto is called as the stereoscopic display device.
In the meantime, the stereoscopic display device can be sorted depending on elements of the lens which implement 3D (3-dimension). As an example, a system in which the lens has a liquid crystal layer is called as a liquid crystal lens electrically driven system.
In general, a liquid crystal display device is provided with two electrodes facing each other, and a liquid crystal layer disposed therebetween, in which liquid crystal molecules are driven by an electric field formed by application of a voltage to the two electrodes. The liquid crystal molecules have a polarizing characteristic and an optical anisotropy. The polarizing characteristic is a characteristic in which, if the liquid crystal molecule is placed in an electric field, electric charge in the liquid crystal molecule is driven to opposite sides of the liquid crystal molecule varying a molecular arrangement direction with the electric field, and the optical anisotropy is variation of a path or a polarization state of light from the liquid crystal layer with a direction of incident of a light or a state of polarization owing to a long and thin structure of the liquid crystal molecule or the molecular arrangement direction described before.
According to this, the liquid crystal layer varies transmissivity with the voltage applied to the two electrodes, and an image can be displayed by varying the difference with pixels.
Recently, a liquid crystal lens electrically driven has been suggested in which the liquid crystal layer is made to serve as a lens by using such characteristics of the liquid crystal molecule.
That is, the lens controls paths of incident lights to vary with positions of the paths by using a difference of refractive indices between a substance of the lens and the air. If voltages varied with positions of electrodes are applied to the liquid crystal layer, to form electric field to drive the liquid crystal layer, the lights incident on the liquid crystal layer sense phases varied with positions of the incident, enabling the liquid crystal layer to control the paths of the incident lights, like an actual lens.
A related art liquid crystal lens electrically driven will be described with reference to the attached drawings.
FIG. 1 illustrates a section of a related art liquid crystal lens electrically driven, and FIG. 2 illustrates a diagram showing a potential distribution after application of a voltage at the time of formation of the liquid crystal lens electrically driven in FIG. 1.
Referring to FIG. 1, the related art liquid crystal lens electrically driven is provided with first and second substrates 10 and 20 facing each other, and a liquid crystal layer formed between the first and second substrates 10 and 20.
The first substrate 10 has first electrodes 11 at first intervals formed thereon. Between adjacent first electrodes 11, a distance between a center of a first electrode 11 on one side to a center of the first electrode on the other side is called as a pitch, and identical patterns (the first electrodes) are formed repeatedly at fixed intervals of the pitch.
The second substrate 20 over and facing the first substrate 10 has a second electrode 21 formed on an entire surface thereof.
The first and second electrodes 11 and 21 are formed of a transparent metal. In a space between the first and second electrodes 11 and 21, the liquid crystal layer 30 is formed, and the liquid crystals of the liquid crystal layer 30 have a parabolic potential surface owing to characteristics of the liquid crystal molecules reactive to intensity and distribution of the electric field, showing a phase distribution similar to the liquid crystal lens electrically driven in FIG. 2.
The liquid crystal lens electrically driven, formed under the condition that a high voltage is applied to the first electrode 11 and the second electrode 21 is grounded, forms the strongest vertical electric field at a center of the first electrode 11 which becomes the weaker as the lens goes the far from the first electrode 11 the more. Accordingly, if the liquid crystal molecules of the liquid crystal layer 30 has a positive dielectric anisotropy, the liquid crystal molecules becomes to have an arrangement according to the electric field in which the liquid crystal molecules are upright at the center of the first electrode 11, and tilted the more close to horizontal direction as the lens goes far from the first electrode 11 the more. Therefore, referring to FIG. 2, in view of transmission of the light, an optical path is short at the center of the first electrode 11 and the optical path becomes the longer as the lens goes far from the first electrode 11 the more. If above is expressed in the phase surface, the liquid crystal lens electrically driven becomes to have an optical transmission effect which is similar to a lens having a parabolic surface.
In this instance, the second electrode 21 induces behavior of the liquid crystal lens electrically driven, making a refractive index the light senses on the whole to be a spatial parabolic function and the first electrode 11 to form an edge region of the lens.
In this instance, the first electrode 11 has a voltage more or less higher than the second electrode 21, such that, as shown in FIG. 2, a potential difference takes place between the first electrode 11 and the second electrode 21, particularly causing a sharp side electric field at a portion of the first electrode 11. According to this, the liquid crystals form, not a moderate distribution, but a more or less distorted shape of distribution, failing to form the spatial parabolic surface of the refractive index, or move very sensitive to the voltage.
The liquid crystal lens electrically driven can be obtained by providing the liquid crystals, forming electrodes on facing substrates with the liquid crystals disposed therebetween, and applying a voltage thereto, without providing a parabolic surfaced lens, physically.
However, the related art liquid crystal lens electrically driven has the following problems.
First, the first electrode formed at a very small portion of the lens region on the lower substrate causes to form an electric field between the lens edge region opposite to the electrode and the lens center region which is far from the lens edge region, not moderately, but to have a sharp side surface electric field to form a more or less distorted liquid crystal lens electrically driven. Particularly, since an electrode having a high voltage applied thereto is limited as the pitch of the lens regions increases the more, making the electric field applied to the lens region between the electrode having a high voltage applied thereto and the facing substrate inadequate, formation of the liquid crystal lens electrically driven having a moderate parabolic surface which has an effect identical to a lens becomes difficult.
Second, as a size of the device becomes the larger, the control of the liquid crystal arrangement becomes the more difficult by using the electric field since the lens center region which is far from the edge region of the lens region at which the electrode having the high voltage applied thereto exists has almost no effect of the electric field.
Third, the liquid crystal lens electrically driven produces only two views in one lens cell. That is, two pixels of the lower display panel are arranged within one pitch at the lens region, forming lenses limited to each pitch on a side the electrode is patterned, to require to increase a number of views of the liquid crystal lens electrically driven within one liquid crystal lens electrically driven for making a variety of display, and changing a number of views.